This study provides a detailed comparison of the different roles and impacts of two distinct types of aquatic animals in inland water systems. It examines their ecological contributions, interactions, and effects on environmental services. The research synthesizes evidence from various global sources, with a focus on Africa and specific applications in Nigeria, to explore their functional roles, ecological pressures, and socio-economic aspects. A systematic review of literature was used, incorporating empirical studies, case analyses, and thematic assessments. The study emphasizes identifying key ecological mechanisms, recording habitat impacts, evaluating new monitoring technologies, and suggesting adaptive management strategies.
The findings show that species established within ecosystems over long evolutionary periods are essential for maintaining nutrient cycling, trophic stability, habitat complexity, and biodiversity resilience. Conversely, recently introduced species, though sometimes providing short-term functional or economic benefits, generally cause ecological disturbances through predation, competition, hybridization, habitat destruction, and pathogen transfer. Interactions between these two groups can produce complex and context-dependent results, sometimes partly compensating for lost functions but often compromising long-term ecological integrity. Technological advances—including environmental DNA metabarcoding, passive acoustic monitoring, biotelemetry, parasite community profiling, and decision-support systems—are seen as transformative tools for detection, assessment, and monitoring, though their widespread use is limited by governance, funding, and capacity challenges.
The study concludes that protecting the stability and productivity of these aquatic systems requires integrated and adaptable strategies that combine ecological restoration with socio-economic considerations. Recommendations emphasize strengthening monitoring systems, adopting more advanced assessment tools, implementing inclusive governance models, and incorporating ecosystem service valuation into policy and management. By aligning conservation goals with human needs, sustainable management of these systems is possible despite the challenges caused by biological invasions.